Exclusion Criteria: discernable anomaly of the anterior chamber, uveitis, significant opacification of the cornea or crystalline lens, eyes with secondary glaucoma, eyes with pigmentary or pseudoexfoliation glaucoma, concurrent active eye disease in the study eye that may affect intraocular pressure or its measurement, patients on kidney dialysis, eyes with proliferative or severe nonproliferative retinopathy, retinal detachment, retinitis pigmentosa, or other significant retinopathy, eyes with field loss attributed to a non-glaucoma condition, dilated pupil diameter less than 4mm, and visual fields < 20 degrees.